1. Field of the Invention
The present invention relates to an apparatus for forming an image, which is used as either a copying apparatus or a printer.
2. Description of the Related Art
Two types of apparatuses for copying an original are known. They are an electronic copier and a printing machine. Either type of a copying apparatus has advantages and disadvantages.
The printing machine is advantageous in that, although it requires a printing plate prepared from an original, the machine can make a great number of copies of the original at high speed by using the plate. The more copies are made, the less the printing cost. The electronic copier is advantageous since no complex preparation is required for copying the original, and thus is easy to operate.
The printing machine is disadvantageous in the following respect. The machine requires the plate to print copies, so that it takes more time to prepare for the copying of the original.
The electronic copier is disadvantageous, also in the following respect. The copying speed is much lower than the printing speed of the printing machine, since the sequence of processes, such as charging the photosensitive drum, scanning the original, developing the image, and discharging the drum, must be repeated to make each copy.
Various methods of copying an original have been proposed. Japanese Patent Publication No. 37-16098 disclosed a method wherein magnetic material is used to copy an original. In this method, the magnetic material is fixed on a photosensitive member, thus forming a fixed image, then other magnetic material is attracted onto the fixed image, and finally the other magnetic material is transferred onto a recording medium. There is a demand for an apparatus which employs such a copying method and can make, at high speed, a copy of an original which is clear and uniform in quality even if the original has fine lines and large black-out portions.